The present invention relates to wellbore tools and more particularly to an apparatus for retrieval of metal objects, such as cuttings and other foreign objects that accumulate in the process of perforating or milling over bridge plugs and other down hole obstructions from a wellbore.
Various types of bridge plugs are conventionally used in the oil and gas industry. These bridge plugs are installed in the annulus and are often covered in cement. Removal of such plugs can sometimes pose a problem for the industry. A rotary bit drills the cement and plugs out, while some of the cuttings of the plugs are carried out to the surface by a liquid circulated down hole.
Sometimes, a production packer needs to be removed together with the metal pipe that it surrounds. In those cases, milling tools with gravity fed boot baskets are used for retrieving pieces of metal from the wellbore. After retrieval of the production packer, it may become necessary to run a conventional fishing magnet to retrieve additional junk and cuttings.
A conventional fishing magnet is mounted inside a housing that is lowered into a wellbore. It is limited in the ability to retrieve cuttings in that its magnetization is restricted to the extreme bottom surface of the magnet. The fact that circulating fluids lift the cuttings away from the bottom surface of the magnet renders that conventional fishing magnet useless in this situation.
Often times, a boot basket is used for collecting cuttings that did not attach themselves to the conventional magnet. A boot basket has small openings for catching these particles. Consequently, many large size pieces or very small pieces suspended in the fluid flow are not trapped in the basket and remain in the wellbore.
The present invention contemplates elimination of drawbacks associated with the prior art and provision of a wellbore apparatus for removal of metal objects, such as cuttings, and other foreign particles that provides for the use of sets of magnets spaced longitudinally along the tool body.